Conventionally, in machines of the aforementioned type, containers are caused to advance by a revolving carousel that presents a disc carrying a plurality of pedestals equispaced angularly around the periphery and serving each to support a respective container; each pedestal is power-driven and rotatable about the axis of the relative container.
The path along which the containers are directed by the conveyor passes through labelling or marking stations where a fixed and predetermined portion of the lateral surface presented by the container will be offered to each such station.
To the end of controlling the angular position of the containers positioned on the pedestals so that they will always be correctly aligned when brought into the labelling or marking stations, the prior art embraces the use of optical sensors connected to a control unit piloting the operation of the motors associated with the single pedestals.
More exactly, the optical sensors in question can be photocells capable of detecting a notch presented by each container, for example, or TV cameras able to process more complex reference images.
It will be observed however that in the case of photocell type sensors, each container must be provided with a reference notch located in a clearly visible position, and there are constraints also on the geometry of the container, which for example cannot have sharp edges, whilst the external surface must be treated so as to render it non-reflective as far as possible, and with colors that will ensure the reference elements are easily read. This means a restricted range of application and limited reliability, especially with successive changes in the size, shape and specifications of containers.
In the case of TV cameras, on the other hand, it should be emphasized that this solution is penalized by excessively high cost, also by the fact that sophisticated and complex image-processing systems are required, and is therefore unsuitable for monitoring operations in machines of the type in question. In addition, it will be appreciated that a television camera is able to operate only in certain conditions of brightness and with a given level of reflection from the surface of the container.
The object of the present invention is to provide a labelling and/or marking machine unaffected by the drawbacks mentioned above.